DUBAI, United Arab Emirates (AP) — A prominent Shiite cleric in Bahrain who led a now-shuttered opposition party was acquitted Thursday of spying charges with two colleagues, marking a rare victory for activists in the island kingdom amid a yearslong clampdown on dissent.

Sheikh Ali Salman headed the Al-Wefaq political party, the largest Shiite opposition group in the kingdom, and served as a central figure in Bahrain’s 2011 Arab Spring protests.

A lawyer previously involved with Salman’s case, Abdulla al-Shamlawi, said the cleric would be released in December after he finished serving some four years in prison in another case widely criticized internationally.

Prosecutors later issued a statement saying they planned to appeal, alleging there was “strong evidence” against the three men.

Activists praised the court decision, but said Salman should be immediately freed.

“Sheikh Ali Salman had been used as a pawn in Bahrain’s game of power politics,” said Sayed Ahmed Alwadaei, the director of advocacy at the Bahrain Institute for Rights and Democracy. “Despite his acquittal, Sheikh Salman will continue to languish in Jaw Prison for exercising his right to freedom of expression.”

Salman, 52, long has been targeted by Bahrain’s government. In 1994, he was arrested, tortured and detained for months without trial before being deported and forced to live in exile for over 15 years, according to the United Nations.

He was a prominent figure in Bahrain’s Arab Spring protests in 2011, in which the island’s Shiite majority and others demanded more freedoms from the Sunni monarchy.

In December 2014, two days after being re-elected as Al-Wefaq’s secretary-general, Salman was again arrested by security forces. This time, prosecutors brought him to trial on charges he insulted the Interior Ministry, which oversees police, incited others to break the law and incited hatred against naturalized Sunni citizens, many of whom serve in the island’s security forces. While Bahrain’s constitution guarantees freedom of expression, authorities routinely arrest and charge activists over their comments.

The U.N.’s Working Group on Arbitrary Detentions issued a report in November 2015 criticizing the arrest and calling for Salman’s release. The report also described its decision as “only one of several opinions that have found Bahrain to be in violation of its international human rights obligations.”

In Thursday’s case, Salman and two other officials from Al-Wefaq, Sheikh Hassan Ali Juma Sultan and Ali Mahdi Ali al-Aswad, faced spying charges. The charges came after Bahrain state television in August aired recorded telephone calls between Salman and Qatar’s then-Prime Minister Sheikh Hamad bin Jassim Al Thani during the 2011 protests. It remains unclear who gave state television the recordings, though activists suspect the island’s intelligence services leaked the call.

Bahrain is one of four Arab countries that have been boycotting Qatar for over a year as part of a wider diplomatic dispute.

The call between Salman and the Qatari official at the time were aimed at peacefully resolving the 2011 protests, which ended when Bahraini, Emirati and Saudi security forces violently put down the demonstrations. A government-sponsored report on the 2011 protests and unrest noted Bahrain’s opposition accepted that mediation while Bahrain’s government rejected it.

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